The present invention generally relates to a multi-access laser communications terminal, and more particularly to a multi-access laser communications terminal having one or more deformable mirrors for steering laser beams to corresponding receivers.
A multi-access laser communications terminal allows one or more devices to send data to the communications terminal using modulated laser beams. For example, a multi-access laser communications terminal can be mounted on a satellite or high-altitude airship and configured to receive data transmitted from vehicles both in the air and on the ground. Devices mounted on the vehicles modulate a laser beam in accordance with data to be sent and transmit the modulated laser beam to the communications terminal. The communications terminal receives the modulated laser beam using an optical fiber receiver and converts the modulated laser beam into an electronic data format which can be processed and stored.
FIG. 1 is a schematic diagram depicting the basic components of a conventional multi-access laser communications terminal. The communications terminal 100 comprises a telescope 110, a mirror 120 and a receiver 130. Beam source 140 transmits a modulated laser beam 150 to the communications terminal 100. The telescope 110 receives the modulated laser beam 150. The modulated laser beam 150 is deflected by the mirror 120. The deflected modulated laser beam 150 is directed to the receiver 130.
In order to receive the data transmitted by the beam source 140, the modulated laser beam 150 must be kept locked on the receiver 130. However, beam sources are often located on vehicles, such as aerial vehicles, that are often in motion when transmitting the modulated laser beam 150. This motion causes the deflected modulated laser beam 150 to drift from the receiver 130 which can result in loss of the data being transmitted.
Various mechanisms have been devised to keep the modulated laser beam 150 locked on the receiver 130. For example, a MEMS (micro-electromechanical) mirror array might be used to steer the modulated laser beam 150 to the receiver 130. However, the use of a MEMS mirror array introduces loss into the system due to the fill factor of the mirror array.
Alternatively, mechanical actuators might be used to alter the position of the receiver 130 in order to keep the modulated laser beam 150 locked on the receiver 130. While this method avoids the losses associated with a MEMS mirror array, proximity issues arise when multiple beam sources get too close to each other.
Hence, it would be desirable to provide methods and systems that are capable of keeping a modulated laser beam locked on a receiver in a laser communications terminal in a more effective manner.